Study On Construction And Properties Of Functional Particle Composite Nanofiber Membrane For Oil/Water Emulsion Separation

With industrial development,the discharge of a large amount of oily wastewater has seriously affected the ecological environment and human health.Among them,oily wastewater from textile,leather and food processing industries usually contains a large number of surfactants and dyes,so the oils are emulsified by surfactants into microemulsified oil with small size and high stability.Traditional oil-water separation technology for oil water separation requires huge costs and low efficiency.In addition,industrial wastewater often contains dyes,bacteria and other organic substances.Aiming at the issues of effectively treating oily wastwater with various pollutants（oil,bacteria and dyes）,we designs and constructs a functional nanofiber membrane by combining electrospun nanofiber membrane with functional nanomaterials,and systematically studies its oil-water separation,antibacterial and dye removal performance.1.Preparation of composite nanofibers by coaxial electrospinning and thermal bonding and their separation performance.Nanofibers with core-shell structures were prepared by coaxial spinning technology.The core layer was polyglycolic acid（PGA,melting point 225°C）,and the shell layer was polycaprolactone（PCL,melting point60°C）.The prepared nanosilver（Ag NPs）were sprayed on the surface of nanofiber membrane by electrostatic spraying technology.At a certain temperature,the shell layer was melted,and Ag NPs were bonded to the nanofibers.The laminar velocity ratio of core and shell and heat treatment conditions were optimized,and the appropriate shell thickness was obtained under the condition of velocity ratio of 3:1（PCL:PGA）.At80°C,the best structure for Ag NPs/PCL-PGA was obtained by thermal bonding for 5min.The composite nanofibers had good mechanical properties and Ag NPs bonding stability,and the antibacterial rate against gram-positive Staphylococcus aureus（S.aureus）is above 97%.At the same time,the composite nanofiber membrane can also effectively separate the water-in-decamethylcyclopentasiloxane（D5）emulsion stabilized by sodium dodecyl sulfate（SDS）.Although PCL with a low melting point can be combined with functional nanoparticles by hot melting,the PCL membranes is not applicable in many oil-water systems,which limits their further application.2.Preparation and water purification performance of composite polyacrylonitrile nanofiber membrane with zeolite imidazole skeleton-8@silver nanocluster.The composite polyacrylonitrile nanofiber membrane（ZIF-8@Ag NCs/PAN）coated with zeolite imidazole framework-8（ZIF-8）and silver nanoclusters（Ag NCs）was prepared by electrospinning and in situ growth techniques.The surface chemical properties,morphology and wettability of the composite nanofiber membrane were characterized by scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,infrared spectroscopy（FTIR）,X-ray diffraction（XRD）,atomic force microscopy（AFM）and contact angle measurements.The carboxyl groups on the surface of hydrolyzed PAN nanofibers（H-PAN）can be complexed with zinc ions(Zn²⁺)and used as the growth sites of porous ZIF-8.In the growth process of ZIF-8,Ag NCs were incoporated into ZIF-8 in situ to obtain the composite nanofiber membrane ZIF-8@Ag NCs/PAN.With the increase of Ag NCs content,the number of ZIF-8@Ag NCs on the fiber surface decreased.When the amount of Ag NCs is 10 m L(ZIF-8@Ag NCs_（10）/PAN),the membrane has high roughness and a stable hydration layer.Therefore,it has high separation performance for various SDS-stabilized oil-in-water emulsions（petroleum ether,toluene,1,2-dichloroethane,chloroform and D5）,among which the flux is 62456±1343 L m^-2 h^-1 bar^-1 and the separation efficiency is 98.6%for petroleum ether-in-water emulsions.In addition,the ZIF-8@Ag NCs/PAN membrane has high antibacterial activity against gram-negative Escherichia coli（E.coli）and S.aureus.However,after many oil-water separations,the particles on the surface of the membrane fell off,and the composite stability of the particles still needs to be improved.3.Zeolite imidazole skeleton-8/polyacrylonitrile@titanium dioxide composite nanofiber membrane for oil/water separation,antibacterial and organic dye removal.Zeolite imidazole skeleton-8/polyacrylonitrile@titanium dioxide（ZIF-8/PAN@Ti O₂）membrane was prepared based on electrospinning technology and in situ growth technology.The morphology,surface chemical properties,physical structure and wettability of the composite membrane were characterized by SEM,FTIR,XRD,laser confocal scanning microscopy and contact angle measurements.Ti O₂ NPs,added to the PAN fibers,provide sites for the growth of ZIF-8.With increasing Ti O₂ content,the diameter of the PAN@Ti O₂ nanofibers increases,and the porosity changes.After in situ growth of ZIF-8,the porosity of composite membrane decreased.However,the membrane obtained a high roughness and stable hydration layer,which is benificial for the effcient separation of SDS-stabilized D5-in-water emulsions.When the doping amount of Ti O₂ was 10 wt%,the composite membrane obtained a high permeation flux(35205±4135 L m^-2 h^-1 bar^-1)and separation efficiency（higher than 99.2%）.In addition,it also showed excellent separation efficiency for various SDS-stabilized oil-in-water emulsions（petroleum ether,toluene,1,2-dichloroethane and chloroform）.Because ZIF-8 particles are loaded on the surface of the fiber membrane,the obtained fiber membrane has excellent antibacterial and dye adsorption properties.